Android 實現GIF播放(解碼)

標籤：

實現原理很簡單，先把GIF動畫解碼成多張Bitmap圖片，然後放到AnimationDrawable裡面去逐一播放即可。

GifHelper代碼：

 

package com.android.view;import java.io.InputStream;import java.util.Vector;import android.graphics.Bitmap;import android.graphics.Bitmap.Config;//Handler for read & extract Bitmap from *.gifpublic class GifHelper {// to define some error typepublic static final int STATUS_OK = 0;public static final int STATUS_FORMAT_ERROR = 1;public static final int STATUS_OPEN_ERROR = 2;protected int status;protected InputStream in;protected int width; // full image widthprotected int height; // full image heightprotected boolean gctFlag; // global color table usedprotected int gctSize; // size of global color tableprotected int loopCount = 1; // iterations; 0 = repeat foreverprotected int[] gct; // global color tableprotected int[] lct; // local color tableprotected int[] act; // active color tableprotected int bgIndex; // background color indexprotected int bgColor; // background colorprotected int lastBgColor; // previous bg colorprotected int pixelAspect; // pixel aspect ratioprotected boolean lctFlag; // local color table flagprotected boolean interlace; // interlace flagprotected int lctSize; // local color table sizeprotected int ix, iy, iw, ih; // current image rectangleprotected int lrx, lry, lrw, lrh;protected Bitmap image; // current frameprotected Bitmap lastImage; // previous frameprotected int frameindex = 0;public int getFrameindex() {return frameindex;}public void setFrameindex(int frameindex) {this.frameindex = frameindex;if (frameindex > frames.size() - 1) {frameindex = 0;}}protected byte[] block = new byte[256]; // current data blockprotected int blockSize = 0; // block size// last graphic control extension infoprotected int dispose = 0;// 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prevprotected int lastDispose = 0;protected boolean transparency = false; // use transparent colorprotected int delay = 0; // delay in millisecondsprotected int transIndex; // transparent color indexprotected static final int MaxStackSize = 4096;// max decoder pixel stack size// LZW decoder working arraysprotected short[] prefix;protected byte[] suffix;protected byte[] pixelStack;protected byte[] pixels;protected Vector<GifFrame> frames; // frames read from current fileprotected int frameCount;// to get its Width / Heightpublic int getWidth() {return width;}public int getHeigh() {return height;}/** * Gets display duration for specified frame. * * @param n *            int index of frame * @return delay in milliseconds */public int getDelay(int n) {delay = -1;if ((n >= 0) && (n < frameCount)) {delay = ((GifFrame) frames.elementAt(n)).delay;}return delay;}public int getFrameCount() {return frameCount;}public Bitmap getImage() {return getFrame(0);}public int getLoopCount() {return loopCount;}protected void setPixels() {int[] dest = new int[width * height];// fill in starting image contents based on last image‘s dispose codeif (lastDispose > 0) {if (lastDispose == 3) {// use image before lastint n = frameCount - 2;if (n > 0) {lastImage = getFrame(n - 1);} else {lastImage = null;}}if (lastImage != null) {lastImage.getPixels(dest, 0, width, 0, 0, width, height);// copy pixelsif (lastDispose == 2) {// fill last image rect area with background colorint c = 0;if (!transparency) {c = lastBgColor;}for (int i = 0; i < lrh; i++) {int n1 = (lry + i) * width + lrx;int n2 = n1 + lrw;for (int k = n1; k < n2; k++) {dest[k] = c;}}}}}// copy each source line to the appropriate place in the destinationint pass = 1;int inc = 8;int iline = 0;for (int i = 0; i < ih; i++) {int line = i;if (interlace) {if (iline >= ih) {pass++;switch (pass) {case 2:iline = 4;break;case 3:iline = 2;inc = 4;break;case 4:iline = 1;inc = 2;}}line = iline;iline += inc;}line += iy;if (line < height) {int k = line * width;int dx = k + ix; // start of line in destint dlim = dx + iw; // end of dest lineif ((k + width) < dlim) {dlim = k + width; // past dest edge}int sx = i * iw; // start of line in sourcewhile (dx < dlim) {// map color and insert in destinationint index = ((int) pixels[sx++]) & 0xff;int c = act[index];if (c != 0) {dest[dx] = c;}dx++;}}}image = Bitmap.createBitmap(dest, width, height, Config.ARGB_4444);}public Bitmap getFrame(int n) {Bitmap im = null;if ((n >= 0) && (n < frameCount)) {im = ((GifFrame) frames.elementAt(n)).image;}return im;}public Bitmap nextBitmap() {frameindex++;if (frameindex > frames.size() - 1) {frameindex = 0;}return ((GifFrame) frames.elementAt(frameindex)).image;}public int nextDelay() {return ((GifFrame) frames.elementAt(frameindex)).delay;}// to read & parse all *.gif streampublic int read(InputStream is) {init();if (is != null) {in = is;readHeader();if (!err()) {readContents();if (frameCount < 0) {status = STATUS_FORMAT_ERROR;}}} else {status = STATUS_OPEN_ERROR;}try {is.close();} catch (Exception e) {e.printStackTrace();}return status;}protected void decodeImageData() {int NullCode = -1;int npix = iw * ih;int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi;if ((pixels == null) || (pixels.length < npix)) {pixels = new byte[npix]; // allocate new pixel array}if (prefix == null) {prefix = new short[MaxStackSize];}if (suffix == null) {suffix = new byte[MaxStackSize];}if (pixelStack == null) {pixelStack = new byte[MaxStackSize + 1];}// Initialize GIF data stream decoder.data_size = read();clear = 1 << data_size;end_of_information = clear + 1;available = clear + 2;old_code = NullCode;code_size = data_size + 1;code_mask = (1 << code_size) - 1;for (code = 0; code < clear; code++) {prefix[code] = 0;suffix[code] = (byte) code;}// Decode GIF pixel stream.datum = bits = count = first = top = pi = bi = 0;for (i = 0; i < npix;) {if (top == 0) {if (bits < code_size) {// Load bytes until there are enough bits for a code.if (count == 0) {// Read a new data block.count = readBlock();if (count <= 0) {break;}bi = 0;}datum += (((int) block[bi]) & 0xff) << bits;bits += 8;bi++;count--;continue;}// Get the next code.code = datum & code_mask;datum >>= code_size;bits -= code_size;// Interpret the codeif ((code > available) || (code == end_of_information)) {break;}if (code == clear) {// Reset decoder.code_size = data_size + 1;code_mask = (1 << code_size) - 1;available = clear + 2;old_code = NullCode;continue;}if (old_code == NullCode) {pixelStack[top++] = suffix[code];old_code = code;first = code;continue;}in_code = code;if (code == available) {pixelStack[top++] = (byte) first;code = old_code;}while (code > clear) {pixelStack[top++] = suffix[code];code = prefix[code];}first = ((int) suffix[code]) & 0xff;// Add a new string to the string table,if (available >= MaxStackSize) {break;}pixelStack[top++] = (byte) first;prefix[available] = (short) old_code;suffix[available] = (byte) first;available++;if (((available & code_mask) == 0)&& (available < MaxStackSize)) {code_size++;code_mask += available;}old_code = in_code;}// Pop a pixel off the pixel stack.top--;pixels[pi++] = pixelStack[top];i++;}for (i = pi; i < npix; i++) {pixels[i] = 0; // clear missing pixels}}protected boolean err() {return status != STATUS_OK;}// to initia variablepublic void init() {status = STATUS_OK;frameCount = 0;frames = new Vector<GifFrame>();gct = null;lct = null;}protected int read() {int curByte = 0;try {curByte = in.read();} catch (Exception e) {status = STATUS_FORMAT_ERROR;}return curByte;}protected int readBlock() {blockSize = read();int n = 0;if (blockSize > 0) {try {int count = 0;while (n < blockSize) {count = in.read(block, n, blockSize - n);if (count == -1) {break;}n += count;}} catch (Exception e) {e.printStackTrace();}if (n < blockSize) {status = STATUS_FORMAT_ERROR;}}return n;}// Global Color Tableprotected int[] readColorTable(int ncolors) {int nbytes = 3 * ncolors;int[] tab = null;byte[] c = new byte[nbytes];int n = 0;try {n = in.read(c);} catch (Exception e) {e.printStackTrace();}if (n < nbytes) {status = STATUS_FORMAT_ERROR;} else {tab = new int[256]; // max size to avoid bounds checksint i = 0;int j = 0;while (i < ncolors) {int r = ((int) c[j++]) & 0xff;int g = ((int) c[j++]) & 0xff;int b = ((int) c[j++]) & 0xff;tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b;}}return tab;}// Image Descriptorprotected void readContents() {// read GIF file content blocksboolean done = false;while (!(done || err())) {int code = read();switch (code) {case 0x2C: // image separatorreadImage();break;case 0x21: // extensioncode = read();switch (code) {case 0xf9: // graphics control extensionreadGraphicControlExt();break;case 0xff: // application extensionreadBlock();String app = "";for (int i = 0; i < 11; i++) {app += (char) block[i];}if (app.equals("NETSCAPE2.0")) {readNetscapeExt();} else {skip(); // don‘t care}break;default: // uninteresting extensionskip();}break;case 0x3b: // terminatordone = true;break;case 0x00: // bad byte, but keep going and see what happensbreak;default:status = STATUS_FORMAT_ERROR;}}}protected void readGraphicControlExt() {read(); // block sizeint packed = read(); // packed fieldsdispose = (packed & 0x1c) >> 2; // disposal methodif (dispose == 0) {dispose = 1; // elect to keep old image if discretionary}transparency = (packed & 1) != 0;delay = readShort() * 10; // delay in millisecondstransIndex = read(); // transparent color indexread(); // block terminator}// to get Stream - Headprotected void readHeader() {StringBuffer id = new StringBuffer();for (int i = 0; i < 6; i++) {id.append((char) read());}if (!id.toString().startsWith("GIF")) {status = STATUS_FORMAT_ERROR;return;}readLSD();if (gctFlag && !err()) {gct = readColorTable(gctSize);bgColor = gct[bgIndex];}}protected void readImage() {// offset of Xix = readShort(); // (sub)image position & size// offset of Yiy = readShort();// width of bitmapiw = readShort();// height of bitmapih = readShort();// Local Color Table Flagint packed = read();lctFlag = (packed & 0x80) != 0; // 1 - local color table flag// Interlace Flag, to array with interwoven if ENABLE, with order// otherwiseinterlace = (packed & 0x40) != 0; // 2 - interlace flag// 3 - sort flag// 4-5 - reservedlctSize = 2 << (packed & 7); // 6-8 - local color table sizeif (lctFlag) {lct = readColorTable(lctSize); // read tableact = lct; // make local table active} else {act = gct; // make global table activeif (bgIndex == transIndex) {bgColor = 0;}}int save = 0;if (transparency) {save = act[transIndex];act[transIndex] = 0; // set transparent color if specified}if (act == null) {status = STATUS_FORMAT_ERROR; // no color table defined}if (err()) {return;}decodeImageData(); // decode pixel dataskip();if (err()) {return;}frameCount++;// create new image to receive frame dataimage = Bitmap.createBitmap(width, height, Config.ARGB_4444);// createImage(width, height);setPixels(); // transfer pixel data to imageframes.addElement(new GifFrame(image, delay)); // add image to frame// listif (transparency) {act[transIndex] = save;}resetFrame();}// Logical Screen Descriptorprotected void readLSD() {// logical screen sizewidth = readShort();height = readShort();// packed fieldsint packed = read();gctFlag = (packed & 0x80) != 0; // 1 : global color table flag// 2-4 : color resolution// 5 : gct sort flaggctSize = 2 << (packed & 7); // 6-8 : gct sizebgIndex = read(); // background color indexpixelAspect = read(); // pixel aspect ratio}protected void readNetscapeExt() {do {readBlock();if (block[0] == 1) {// loop count sub-blockint b1 = ((int) block[1]) & 0xff;int b2 = ((int) block[2]) & 0xff;loopCount = (b2 << 8) | b1;}} while ((blockSize > 0) && !err());}// read 8 bit dataprotected int readShort() {// read 16-bit value, LSB firstreturn read() | (read() << 8);}protected void resetFrame() {lastDispose = dispose;lrx = ix;lry = iy;lrw = iw;lrh = ih;lastImage = image;lastBgColor = bgColor;dispose = 0;transparency = false;delay = 0;lct = null;}/** * Skips variable length blocks up to and including next zero length block. */protected void skip() {do {readBlock();} while ((blockSize > 0) && !err());}public void recycle(){for (int i = 0; i < frames.size(); i++) {frames.get(i).image.recycle();}}// to store *.gif data, Bitmap & delayprivate class GifFrame {// to access image & delay w/o interfacepublic Bitmap image;public int delay;public GifFrame(Bitmap im, int del) {image = im;delay = del;}}}

　　

 

控制項代碼：

 

package com.android.view;import android.content.Context;import android.content.res.TypedArray;import android.graphics.drawable.AnimationDrawable;import android.graphics.drawable.BitmapDrawable;import android.util.AttributeSet;import android.view.View;import com.gifdemo.R;public class GifView extends View {private GifHelper gHelper;private AnimationDrawable animDrawable;public GifView(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stubgHelper = new GifHelper();TypedArray ta = context.obtainStyledAttributes(attrs,R.styleable.GifView);animDrawable = new AnimationDrawable();int resID = ta.getResourceId(R.styleable.GifView_src, -1);gHelper.read(getResources().openRawResource(resID));for (int i = 0; i < gHelper.getFrameCount(); i++) {int delay = gHelper.getDelay(i);if (i == 0)animDrawable.addFrame(new BitmapDrawable(gHelper.getFrame(i)),delay);elseanimDrawable.addFrame(new BitmapDrawable(gHelper.nextBitmap()),delay);}animDrawable.setBounds(0, 0, gHelper.getImage().getWidth(), gHelper.getImage().getHeight());setBackgroundDrawable(animDrawable);ta.recycle();animDrawable.setOneShot(false);animDrawable.start();}public void recycle() {gHelper.recycle();}}

　　

 

attrs.xml源碼：

 

<?xml version="1.0" encoding="utf-8"?><resources>    <declare-styleable name="GifView">        <attr name="src" format="integer" />    </declare-styleable></resources>

　　

Android 實現GIF播放(解碼)